This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 2000-163094 filed on May 31, 2000, the entire content of which is incorporated herein by reference.
This invention generally relates to a driving unit having a pinion gear and a driven gear. More particularly, the present invention pertains to a vehicle seat reclining adjuster that includes a driving unit having a stopper mechanism for defining the rotation range of the driven gear.
A known driving unit for transmitting driving rotation from a pinion gear to a driven gear is disclosed in a Japanese Patent Application published as Toku-Kai-Hei 10 (1998)-014692. This known driving unit includes a pinion gear having a smaller number of teeth than the driven gear. A stopper mechanism for this driving unit has a stopper gear disposed beside the driven gear. The stopper gear has a slightly different number of teeth as compared to the driven gear. Both the driven gear and the stopper gear mesh with the pinion gear. Due to the difference in the number of teeth between the driven gear and the stopper gear, the driven gear and the stopper gears rotate relative to each other according to their rotation to the pinion gear. A stopper projection is formed on the side face of one of the driven gear or the stopper gear and an elongated hole is formed on the side face of the other gear to engage with the elongated hole so as to define the rotation range of the driven gear.
In the stopper mechanism used in this known driving unit, when the driven gear reaches the end of its rotation range, the pinion gear teeth get increased resistance force for meshing with the driven and the stopper gear teeth because the width between the teeth of the driven gear and the stopper gear becomes narrower. Therefore, the gears receive excessive stress when the pinion tooth is forced or thrust in the narrower teeth width.
The gear for the driving unit is formed from plastic material for producing quiet operation and a lightweight construction. However, it is difficult to make the size of the gear smaller while reducing the cost because the teeth suffer from the excessive stress when the rotation range stopper operates.
A need thus exists for a driving unit possessing a stopper mechanism which does not apply excessive stress on the gear teeth.
According to one aspect of the invention, a vehicle seat includes a seat cushion, a seat back, a lower arm secured to the seat cushion and mounted on a shaft, and an upper arm secured to the seat back and mounted on the shaft, with a position of the upper arm relative to the lower arm being adjustable. A driven gear is mounted on the shaft, and a pinion gear possesses an axle portion and a gear portion engaging the driven gear. A stopper mechanism defines a rotation range of the driven gear and includes a transmitting mechanism for applying a stopping force to the axle portion of the pinion gear.
In accordance with another aspect of the invention, a driving mechanism includes a pinion gear having a gear portion and an axle portion, a driven gear rotated by the pinion gear, and a stopper mechanism defining a rotation range of the driven gear. The stopper mechanism includes a transmitting mechanism for applying a stopping force to the axle portion of the pinion gear.
According to a further aspect of the invention, a driving mechanism includes a driven gear mounted on a shaft to rotate together with the shaft, a pinion gear having an axle portion and a gear portion engaging the driven gear, a first element provided on the driven gear, and a second stopper element provided on the pinion gear. The first stopper element and the second stopper element have portions that engage one another at an end of a rotational range of movement of the pinion gear and the driven gear to apply a stopping force to the axle portion of the pinion gear.